CENTROPAGIDAE Giesbrecht, 1893

Boxshall, Geoff A. & Jaume, Damià, 2012, Centropages orsinii Giesbrecht, 1889 (Copepoda, Calanoida, Centropagidae) from an anchialine cave in Vanuatu, Zoosystema 34 (2), pp. 377-387 : 378-382

Family CENTROPAGIDAE Giesbrecht, 1893 Genus Centropages KrØyer, 1849

Centropages orsinii Giesbrecht, 1889 ( Figs 1-5 )

NEW MATERIAL EXAMINED. — Vanuatu, Espiritu Santo, E coast of Cape Queiros, Loren cave, 14°58.850’S, 167°03.553’E, 1 ♂, IX.2006, F. Bréhier, S. Eberhard and N. Lasson (BMNH Reg. no. 2011.1266).

OTHER MATERIAL EXAMINED. — South Arabian coast, stn 56, John Murray expedition, surface net, 1 ♂, 4.XI.1933 (BMNH Reg. no. 1949.12.31.352). — Great Barrier Reef, 5 stations inside reef east of Low Island, stns 45 and 50 outside reef, 10 ♀♀, 8 ♂♂, Great Barrier Reef expedition (BMNH Reg. no. 1948.4.28.72)

TYPE LOCALITY. — Red Sea.

DESCRIPTION OF ADULT MALE

Body ( Fig. 1A ) 1.54 mm in length. Prosome comprising cephalosome and five pedigerous somites: cephalosome and first pedigerous somite separated by complete suture line. Functional articulation retained between somites 4 and 5, with posterolateral corners of pedigerous somite 5 slightly pointed and slightly asymmetrical in dorsal aspect, extending posteriorly further on left side ( Fig. 1B ). Rostrum weakly developed, broadly triangular, with large pair of frontal filaments directed postero-ventrally ( Fig. 1C ). Body widest at first pedigerous somite, ratio of prosome to urosome length c. 2.65: 1. Urosome 4-segmented; genital somite symmetrical, with single gonopore opening posterolaterally on left side ventral surface; somite lacking surface ornamentation. Ratio of lengths of urosomites and caudal rami: 1.00: 1.50:1.23: 1.09: 1.66; anal somite slightly shorter than 2 preceding free abdominal somites; anus opening terminal, located between caudal rami, anal operculum absent. Caudal rami ( Fig. 1B ) symmetrical, 2.3 times longer than wide, with four long plumose setae along distal margin, one medium-length seta distally on outer margin, and one reduced seta (seta VII) located on dorsal surface near inner distal angle; seta I absent.

Antennules ( Fig. 2 ) long and asymmetrical. Left antennule ( Fig. 2 A-C) non-geniculate, extending about to level of second urosomite ( Fig. 1A ), indistinctly 24-segmented with all articulations expressed, except between segments II-IV and XXVI-XXVIII; articulation between segments I and II incompletely expressed. Armature formula as follows: segment 1 (ancestral segment I), 2 + ae; segment 2 (corresponding to compound ancestral segments II-IV), 2 setae + 2 aesthetascs; segment 3 (V), 2 + ae; segment 4 (VI), 2 + ae; segment 5 (VII), 2 + ae; segment 6 (VIII), 1 + ae; segment 7 (IX), 2 + ae; segment 8 (X), 2 + ae; segment 9 (XI) 2 + ae; segment 10 (XII), 2 + ae; segment 11 (XIII), 1 + ae; segment 12 (XIV), 2 + ae; segment 13 (XV), 2 + ae; segment 14 (XVI) to 19 (XXI), 2 + ae, each; segment 20 (XXII), 1 + ae; segment 21 (XXIII), 1 seta; segment 22 (XXIV), 1 + 1; segments 23 (XXV), 1 + 1 + ae; segment 24 (composed XXVI- XXVIII), apical setation incomplete.

Right antennule ( Fig. 2 D-F) geniculate, 21-segmented, but with articulation between segments I and II incompletely expressed as in left antennule. Armature as follows: segment 1 (ancestral segment I), 2 + ae; segment 2 (corresponding to compound ancestral segments II-IV), armature incomplete; segment 3 (V), 2 + ae; segment 4 (VI), 2; segments 5 (VII) to 7 (IX), 2 + ae each; segment 8 (X), 1 + ae; segment 9 (XI) 2 + ae; segments 10 (XII) and 11 (XIII), 1 + ae each; segment 12 (XIV), 1 seta, 1 spine + ae; segment 13 (XV), 2 + ae; segment 14 (XVI), 1 seta, 1 spine + ae; segments 15 (XVII) and 16 (XVIII), 2 + ae, each; segment 17 (XIX), 1 + ae; segment 18 (XX), 1 seta; segment 19 (XXI-XXIII), 1 + 2 modified spines (but scars indicating 2 elements missing); segment 20 (XXIV- XXV), 2 + 2; segment 21 (XXVI-XXVIII), 6 + ae. Spinule rows present on segments XIX and XX, and on segment XXI, either side of geniculation.

Antenna ( Fig.1D ) biramous. Coxa short, bearing plumose seta at distomedial angle. Basis with two subequal plumose setae on distomedial angle.Exopod indistinctly 7-segmented: segmental homologies I, II-IV,V,VI, VII, VIII, IX-X; intersegmental articulations between segments V to VII partially expressed; setal formula as follows: 1, 3, 1, 1, 1, 1, 1 + 3. All setae plumose. Endopod 2-segmented: proximal segment with two unequal, naked setae; compound distal segment expanded into medial lobe bearing seven setae, and with distal portion crowned with seven setae; segment ornamented with transverse row of long spinules subdistally on lateral margin.

Mandibular gnathobase ( Fig. 3B ) with cutting edge comprising eight cuspidate or simple teeth plus dorsal spinulose seta; ventralmost tooth largest, smooth and unicuspid. Ornamented with row of short spinules on surface near teeth. Palp ( Fig. 3A ) biramous, basis with four setae on inner margin, proximalmost seta unipinnate, other three setae naked. Exopod 5-segmented, setal formula 1, 1, 1, 1, 2. Proximal endopodal segment with four setae at distomedial angle; distal segment with nine unequal setae, plus subapical transverse row of spinules.

Maxillule ( Fig. 3 C-D) with praecoxal arthrite carrying ten marginal spines plus four stiff setae on posterior surface. Coxal epipodite with nine setae; coxal endite with three spinulose setae. Basis fused to both rami: armed with four setae on proximal endite; distal basal endite with seven setae; basal exite represented by single vestigial seta. Exopod bearing eleven marginal setae. Endopod indistinctly 2-segmented, setal formula 4, 5.

Maxilla ( Fig. 3E ) indistinctly 7-segmented, comprising partially coalesced praecoxa and coxa, basis and 4-segmented endopod. Armature of praecoxal and coxal endites 5, 3, 3, 3, respectively; all bilaterally spinulate. Basal endite with four setae, one longer than others. Free endopod carrying seven setae in total. Long seta on basis and most setae on endopodal segments sparsely, bilaterally spinulate with spinules increasing in length distally.

Maxilliped ( Fig. 3F ) 7-segmented with syncoxa, basoendopod and free 5-segmented endopod. Syncoxa with 1, 2, 3, 4 setae on medial margin lobes, most setae sparsely bilaterally spinulate; small patch of denticles on medial surface proximal to seta of first syncoxal lobe. Basis about as long as syncoxa, with three plumose setae of basal origin plus two distal setae derived from incorporated first endopodal segment; row of strong spinules present along medial margin of segment proximal to basal setae. Free endopod setal formula: 4, 4, 3, 3 + 1, 4.

Swimming legs 1-4 ( Figs 4 A-C; 5A) biramous, with 3-segmented exopods:endopod 2-segmented in leg 1, indistinctly 2-segmented in legs 2 and 3, and 3-segmented in leg 4. Armature of legs: see Table 1.

Endopods of legs 2 and 3 with articulation between segments 1 and 2 only partially expressed. Inner basal seta on leg 1 short, only reaching to middle seta on compound proximal endopodal segment. Long setae on rami plumose; outer spines on distal exopodal segment of leg 1 flagellate; outer spines on legs 2 to 4 short and stout; terminal spine on exopod of each leg plumose internally and with marginal membrane externally. Outer margins of endopod segments with fine spinule rows; outer margins of second and third exopodal segments with row of fine spinules proximal to first spine. Leg 4 asymmetrical; basis of left leg unmodified, basis of right leg with three digitiform processes on outer and posterior surfaces ( Fig. 5A, B ).

Fifth legs ( Fig. 5C ) strongly asymmetrical. Left leg biramous, with relatively unmodified 3-segmented endopod, setal formula 0-1; 0-1; 2, 2, 2; exopod 2-segmented, heavily sclerotised; first segment with unilaterally serrate outer spine; second segment bearing 2 outer margin spines and with bilaterally serrate distal spine fused to segment; inner margin with spinule row. Right leg biramous, with endopod unmodified, exhibiting same setal formula as for left endopod; right endopod longer and wider than left. Exopod 3-segmented: first segment short, with outer spine and adjacent spinous process located at outer distal angle; second segment with large “thumb” process located proximally on inner margin – thumb process weakly-curved and about 10% longer than segment; outer spine very short and located on posterior surface of segment close to distal margin: third segment forming long, weaklycurved claw (often referred to as “terminal process”) armed with slender seta on medial margin close to basal articulation.

Figures

FIG. 1. — Centropages orsinii Giesbrecht, 1889 adult male: A, habitus, dorsal; B, last prosomite and urosome, dorsal; C, rostrum and frontal filaments, ventral; D, antenna. Scale bars: A, 0.05 mm; B, 250 μm; C, D, 100 μm.

FIG. 2. — Centropages orsinii Giesbrecht, 1889 adult male: A, non-geniculate left antennule, expressed segments 1 to 12; B, left antennule, expressed segments 13 to 17; C, left antennule, expressed segments 18 to 24 (some setal elements missing from apex); D, geniculate right antennule, expressed segments 1 to 13; E, right antennule, expressed segments 14 to 17; F, right antennule expressed segments 18 to 21 (setal elements missing from segment 19, as indicated by scars). Scale bar: 100 μm.

FIG. 3. — Centropages orsinii Giesbrecht, 1889 adult male: A, mandibular palp; B, mandibular gnathobase; C, maxillule, lacking marginal armature from praecoxal arthrite, posterior; D, praecoxal arthrite of maxillule showing margin setation (only insertion sites of posterior setae shown); E, maxilla (with two long endopodal setae drawn truncated for clarity); F, maxilliped. Scale bars: 100 μm.

FIG. 4.— Centropagesorsinii Giesbrecht,1889 adult male:A, leg 1, anterior;B, leg 3,anterior;C, endopod of leg 2,anterior.Scale bars:100 μm.

FIG. 5. — Centropages orsinii Giesbrecht, 1889 adult male: A, leg 4, posterior view showing right leg, with rami of left leg not drawn; B, basis of right leg 4, lateral view showing processes; C, leg 5, posterior view; D, basis of right leg 4 of male from John Murray expedition (BMNH 1949.12.31.352), lateral view showing processes; E, coxa and basis of right leg 4 of male from Great Barrier Reef expedition (BMNH 1948.4.28.72), posterior view showing processes on basis. Scale bars: A-C, 100 μm; D, E; 50 μm.